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Scaphoid fractures: anatomy, diagnosis and treatment

Buijze, G.A.

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Citation for published version (APA):Buijze, G. A. (2012). Scaphoid fractures: anatomy, diagnosis and treatment.

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Download date: 20 May 2020

Management of scaphoid nonunion: current concepts

Buijze GA, Ochtman L, Ring D.

J Hand Surg Am. 2012 May;37(5):1095-100.

13Chapter

Chapter 13

Abstract

The primary risk factor for nonunion of the scaphoid is displacement/instability, but

delayed or missed diagnosis, inadequate treatment, fracture location, and blood supply

are also considered. It seems that untreated nonunion will lead to degenerative wrist

arthritis—the so-called SNAC wrist (scaphoid nonunion advanced collapse). However,

the correlation of symptoms and disease is poor; the true “natural history” is debatable

because we only evaluate symptomatic patients presenting for treatment. It’s not clear

that surgery can change the natural history even if union is obtained. The diagnosis

of nonunion is made on radiographs but CT or MRI scans may be useful to assess

deformity and blood supply. Treatment options vary from percutaneous fixation

to ORIF with vascularized or non-vascularized bone grafting, to salvage procedures

involving excision and/or arthrodesis of carpal bones.

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Introduction

Although the majority of scaphoid fractures heal with nonoperative treatment, the

focus is usually on the approximate 10% nonunion rate in most case series.1 More

recent data confirm that when displacement is accurately diagnosed and adequate

protection provided the union rate approaches 100%.2,3 Fracture displacement

(usually defined as a gap or translation between the fracture fragments) has been

associated with a risk of nonunion up to 55%.4-6

It is tempting to speculate that the nonunions in older series were primarily displaced

fractures. Most published series and clinical trials did not diagnose displacement. The

few that have excluded displaced fractures used radiographs to diagnose displacement,

which are not as reliable as computed tomography.7

Several risk factors for scaphoid nonunion are based more on tradition and wisdom

than on scientific data. Failure to seek medical attention after a fracture (for instance,

assuming it’s just a sprain) is considered a risk factor for scaphoid nonunion.8,9 Many

minimally displaced fractures are not visible on radiographs (at least initially), and these

missed fractures may also be at risk for nonunion.9 Finally, proximal pole fractures

seem to be at higher risk of nonunion and avascular necrosis (AVN). The traditional

explanation for this is a decreased arterial supply to the proximal pole that makes

fractures in that area more likely to progress to nonunion and limits the potential

healing.8

Presentation

Scaphoid fractures are most common in adult men between the ages of 15 to 40 years

and are rare in those under 10 years of age.10 Based on the fact that many patients

present years or decades after fracture and nonunion, it seems safe to assume that

many nonunions are either minimally symptomatic or that patients are able to adapt

to the symptoms. The most common clinical sign of a scaphoid nonunion is restricted

wrist motion but other suggestive findings include tenderness in the anatomic snuff

box or scaphoid tubercle,10 dorsal swelling, persistent pain at the extremes of motion

(especially dorsal flexion), and decreased grip strength.8

Typical radiographic signs of nonunion are widening of the fracture cleft, cyst formation

and sclerosis of the fracture surfaces.9 Given that radiographic diagnosis of union is

unreliable during the first four months after injury,11 the diagnosis of nonunion requires

an interval of at least 6 to 12 months after injury, or perhaps another diagnostic

method such as computed tomography, although to date this is not well studied.12

Magnetic resonance imaging (MRI) is often used to diagnose AVN, especially in the

proximal pole.13 MRI has been reported to have a high correlation with intraoperative

findings (i.e. punctuate bleeding of the proximal pole with the tourniquet released);

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however, there are contradictory data on the ability of MRI to predict the rate of union

after bone grafting.14-16 Moreover, MRI is expensive, not available in all centers and

poor in assessing bony fracture details.17 It’s unclear whether MRI is as good as CT for

evaluation of alignment.

Advantages of CT include its increased availability, lower cost and more detailed

imaging of bony anatomy. A preoperative CT is valuable to analyze the angular

deformity, evaluate the pathologic scapholunate angle, and calculate the resection

and size of the graft needed.

There are two different patterns of displacement, volar and dorsal.18 The location

of the fracture line relative to the dorsal apex of the ridge of the scaphoid seems to

determine the nonunion pattern and the development of a dorsal intercalated segment

(DISI) deformity.18,19 The volar-type is usually seen in relatively distal scaphoid waist

fractures in which the scaphoid forms a humpback deformity and the bone defects

are large and triangular and are mostly seen along with a DISI deformity. The dorsal-

type is seen in relatively proximal waist fractures in which the bone defects are much

smaller and a flat, crescent-shaped pattern is seen (Figure 1).20 Another recent study

showed that a preoperative longitudinal CT of scaphoid nonunion is can be helpful

in identifying AVN and predicting subsequent fracture union.21 The two signs that

significantly correlated with AVN were increased radiodensity of the proximal pole

(often termed sclerosis) and the absence of converging trabeculae between the

fragments. Increased radiodensity of the proximal pole on CT had a sensitivity of

60%, a specificity of 100% and an accuracy of 74% for diagnosing histologically

proved AVN; thus this sign seems a good diagnostic method to rule in but not to rule

out AVN.

Scaphoid nonunions can be defined as stable or unstable. In stable nonunions the

length and shape of the scaphoid are preserved and there is a firm fibrous connection

between the fracture fragments.8 It is not clear whether stable, well aligned nonunions

lead to arthrosis or cause symptoms.

Unstable nonunion show a distinct pattern of degenerative changes eventually leading

to a scaphoid nonunion advanced collapse (SNAC) wrist. Initially, a DISI deformity

of the wrist is commonly seen and may progress over time. Degenerative changes

typically occur between the radius and distal scaphoid fragment first and eventually in

the midcarpal joint, particularly between the capitate and proximal scaphoid fragment

and between the lunate and capitate (Figure 2). The articulation of the proximal

scaphoid fragment and the lunate with the distal radius is relatively spared.

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Nonunion Treatment

The goals of treatment for scaphoid nonunion include union, correction of deformity,

relief of symptoms, and limitation of arthrosis.8 The main factors that adversely affect

outcome in scaphoid nonunion include a long duration of nonunion, no punctate

bleeding of the proximal pole with the tourniquet released at surgery, and failed

previous surgery.22

Surgery for scaphoid nonunion has short-term and long-term goals; however, most

studies focus on union alone and not much is known about the ability of surgery

for scaphoid union to diminish symptoms in the short term and limit arthrosis in the

long-term. One study23 reported a 97% rate of degenerative changes in thirty-two

untreated symptomatic nonunions older than 5 years and another study found a clear

correlation between increased degenerative changes and the duration of nonunion.24

There is good evidence that scaphoid nonunion is associated with progressive

degenerative changes, although there is wide variation in both the rate of progression

and the associated symptoms. However, it is not so clear that these degenerative

Figure 1A The volar type of scaphoid nonunion as seen from the lateral view showing the direction of fracture displacement (solid arrows) and the inferred contact area between the distal fragment of the scaphoid and the radius (open arrows). B The dorsal type of scaphoid nonunion as seen from the lateral view showing the direction of fracture displacement (solid arrow) and the inferred contact area between the distal fragment of the scaphoid and the radius (open arrows). Reprinted from Moritomo H, Viegas SF, Elder KW, Nakamura K, Dasilva MF, Boyd NL, et al. Scaphoid nonunions: a 3-dimensional analysis of patterns of deformity. J Hand Surg Am. 2000; 25:520-528. (The Journal of Hand Surgery has copyright permission.)

A

B

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Figure 2A-D. Radiographs of an untreated and ununited scaphoid fracture illustrating the natural course of the degenerative process over several decades. Note the typical aspects of progression of a scaphoid nonunion advanced collapse (SNAC) including radioscaphoid osteoarthritis of the distal pole, dorsal intercalated segment instability (dorsal flexion of lunate) and avascular necrosis of the proximal pole.

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changes arrest when union is achieved. Long-term follow-up studies (with a minimum

of 5 years follow-up) suggest that, on average, the progression of arthrosis is slower in

patients that have achieved union than in patients who have an untreated nonunion,

but this is very difficult to study in an unbiased way.25-27

When the interval between injury and presentation is either several years or unknown,

arthrosis may already be established—whether radiographically visible or not. Surgeons

debate when salvage procedures (surgery that changes the anatomy of the wrist with

the goal of symptom control) are favored over attempts to gain union.

Internal fixation without bone grafting

Percutaneous screw fixation without bone grafting has been suggested for stable

or nascent (meaning less than 6 months) nonunions. The findings of a few small

series published in preliminary form suggested that percutaneous repair of selected

well-aligned scaphoid delayed unions and nonunions requires only rigid fixation to

achieve healing.28,29 To our knowledge, no fully peer-reviewed publications have

addressed percutaneous treatment of stable well-aligned nonunions for that matter.

Non-vascularized bone grafting

The Matti-Russe procedure is the traditional treatment for scaphoid nonunion and some

series suggest that the results correlate only with union and not with alignment.27,30

The Matti-Russe technique consists of a volar approach in which the nonunion is

excavated with either hand or power-driven instruments, and the defect is packed

with cortical struts and cancellous bone. Fixation with K-wires is recommended only

when the scaphoid does not move as a unit after placement of the graft, otherwise it

is optional. This procedure does not allow for accurate restoration of alignment.

Fisk followed by Fernandez suggested an anterior wedge graft intended to improve

alignment of the scaphoid and decrease the dorsal tilt of the lunate.31 Preoperative

planning is used to measure the normal scaphoid to determine the amount of bone

to be resected and the size and shape of the bone graft. Both the Matti-Russe and

Fisk-Fernandez techniques emphasize the need to resect substantial portions of the

scaphoid fracture surfaces in order to encourage healing, under the rationale that the

sclerotic fracture ends will not support healing.

An attempt is made to use small screws, but Kirschner wires are acceptable and may

be needed in revision cases where there is bone loss from a loose screw. Union

rates of 80-90% can be achieved.30,32,33 In a structured review of unstable nonunion

series, screw fixation with grafting (94% union) was superior to K-wires and wedge

grafting (77% union).34

One retrospective comparative study of non-vascularized grafts from different sources

has been performed for treatment of scaphoid nonunions.22 This study showed no

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significant differences in union rate between grafts harvested at the iliac crest and

grafts harvested at the dorsal side of the distal radius.

There is debate about the role of non-vascularized grafts in nonunions with AVN, as

the Matti-Russe procedure has been associated with higher failure rates in cases of

diminished or absence of punctuate bleeding at surgery.33 Other disadvantages are

postoperative short-term donor site morbidity, longer surgery, and technical demands

of the carved grafts.35

Vascularized bone grafting

Vascularized bone grafts can be derived from several different locations. The most

commonly used bone grafts are from the distal radius. One method of trying to

enhance the vascular supply to an ununited fracture of the scaphoid is the superficial

radial artery pedicle (Hori technique). In 1979, Hori et al. initially described active

proliferation of blood vessels and new-bone formation when a bundle consisting of

an artery, venae comitantes, and perivascular tissue was implanted into the bone

in a canine model.36 In 1988, Kawai and Yamamoto reported on a volar pronator

quadratus pedicle with which they achieved union in all eight patients with a scaphoid

non-union. In 1995, Fernandez and Eggli reported on eleven patients with scaphoid

nonunion who were managed with inlay bone-grafting, internal fixation, and

implantation of a vascular pedicle from the second dorsal intermetacarpal artery.37

Union was achieved in ten patients at an average of ten weeks postoperatively.

In 1991, Zaidemberg et al. reported on a pedicle from the radial aspect of the distal

radius including the 1,2 intercompartmental supraretinacular artery (1,2-ICSRA,

Zaidemberg technique).38 They achieved union in all eleven cases, with an average

time to union of 6.2 weeks. In 2002, Steinmann et al. reported on the use of a

1,2-ICSRA pedicle in fourteen nonunions which all healed at a mean of 11.1 weeks39.

Conversely, Straw et al. only achieved union in six (27%) of the 22 fracture nonunions

with this technique after a follow-up of 1 to 3 years40. In 2006, Chang et al. reported

on 48 scaphoid fractures treated with the 1,2-ICSRA pedicled vascularized bone graft

of which 34 healed at an average of 15.6 weeks after surgery (71%).41 In 2009,

Waitayawinyu et al. reported on 30 scaphoid nonunions with MRI-documented

proximal pole AVN treated with the 1,2-ICSRA pedicle of which 28 united after an

average of 5.1 months.42

Thus, the reports on the use of distal radial pedicle grafts vary greatly in terms of

success, with union rates ranging from 27% to 100%.38-40 Similar to the outcomes

of treatment with non-vascularized grafts, higher union rates are usually obtained in

absence of AVN.41 However, the use of a wide range of definitions of AVN (or the lack

thereof) makes a valid comparison between series difficult.

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Recently, free vascularized bone grafts have been reported from the iliac crest and

the medial femoral supracondylar region with similar results in terms of union rates.43-

45 One retrospective comparative study of vascularized grafts has been performed

and this study showed a significantly higher union rate and shorter time to healing for

nonunions treated with the medial femoral condyle graft compared to the 1,2-ICSRA

pedicle graft.46

There is one randomized controlled trial comparing vascularized to non-vascularized

bone grafting for scaphoid nonunion.47 In this study, 35 patients were allocated to

treatment with a vascularized 1,2-ICSRA pedicle graft, and 45 to treatment with a

non-vascularized iliac crest graft. All patients in the non-vascularized group healed,

whereas three patients in the vascularized group failed to heal, all of which were

related to technical difficulties. There were no significant differences between the

groups in union rates, time to union and functional results, with the exception of a

small and likely clinically insignificant greater radial deviation in the vascularized group.

Pediatric Nonunions

Scaphoid fractures in children are very uncommon.48 Because of the high amount of

cartilage present in the scaphoid in the immature skeleton, most fractures appear in

the distal third and therefore nonunion is rare.49 Optimal treatment is debated.50

Most pediatric nonunion studies evaluated operative treatment,49,51,52 but successful

conservative treatment has also been reported.53 All series evaluating operative

treatment have shown excellent results and few complications, and independent of

the type of internal fixation, the use of additional bone graft, or bone graft without

internal fixation.49-51,54,55 These data show a great prognosis for children with this

injury.

Revisions and salvage procedures

When surgery for nonunion is unsuccessful, bone stock and bone quality are further

compromised, which may undermine conditions for further corrective surgery.56

Another attempt to gain healing may be considered if there is felt to be adequate

bone and minimal arthrosis.56

A salvage procedure is considered when union cannot be achieved after one or more

attempts or when arthrosis becomes established.8 Salvage options include wrist

denervation, radial styloidectomy, excision of the distal pole of the scaphoid, proximal

row carpectomy (PCR), scaphoid excision and so-called “four-corner” arthrodesis

(capitate, hamate, triquetrum, and lunate), and total wrist arthrodesis. The data

regarding each option are limited and there are advocates of each.

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Summary

The scaphoid is notorious for trouble with healing. It seems that the majority of these

are unstable and malaligned. There are many variations to nonunion surgery, which

reflects the lack of satisfaction or consistency with any one strategy. Areas of debate

include the role of vascularized bone grafts and the transition from attempts to gain

union to salvage procedures.

Acknowledgements:

The authors would like to thank Dr. G.R. Schaap for providing the historical illustrations.

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15. Singh AK, Davis TR, Dawson JS, Oni JA, Downing ND. Gadolinium enhanced MR assessment of proximal fragment vascularity in nonunions after scaphoid fracture: does it predict the outcome of reconstructive surgery? J Hand Surg Br 2004;29(5):444-8.

16. Megerle K, Worg H, Christopoulos G, Schmitt R, Krimmer H. Gadolinium-enhanced preoperative MRI scans as a prognostic parameter in scaphoid nonunion. J Hand Surg Eur Vol. 2011;36(1):23-8.

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19. Oka K, Moritomo H, Murase T, Goto A, Sugamoto K, Yoshikawa H. Patterns of carpal deformity in scaphoid nonunion: a 3-dimensional and quantitative analysis. J Hand Surg Am 2005;30(6):1136-44.

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41. Chang MA, Bishop AT, Moran SL, Shin AY. The outcomes and complications of 1,2-intercompart-mental supraretinacular artery pedicled vascularized bone grafting of scaphoid nonunions. J Hand Surg Am 2006;31(3):387-96.

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47. Braga-Silva J, Peruchi FM, Moschen GM, Gehlen D, Padoin AV. A comparison of the use of distal radius vascularised bone graft and non-vascularised iliac crest bone graft in the treatment of non-union of scaphoid fractures. J Hand Surg Eur Vol 2008;33(5):636-40.

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51. Chloros GD, Themistocleous GS, Wiesler ER, Benetos IS, Efstathopoulos DG, Soucacos PN. Pediatric scaphoid nonunion. J Hand Surg Am 2007;32(2):172-6.

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54. Garcia-Mata S. Carpal scaphoid fracture nonunion in children. J Pediatr Orthop 2002;22(4):448-51.

55. Mintzer CM, Waters PM. Surgical treatment of pediatric scaphoid fracture nonunions. J Pediatr Orthop 1999;19(2):236-9.

56. Reigstad O, Thorkildsen R, Grimsgaard C, Reigstad A, Rokkum M. Is revision bone grafting worth-while after failed surgery for scaphoid nonunion? Minimum 8 year follow-up of 18 patients. J Hand Surg Eur Vol 2009;34(6):772-7.

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